1. Field of the Invention
The present invention relates to a Low Temperature Co-fired Ceramic (LTCC) composition, an LTCC substrate comprising the same, and a method of manufacturing the same, and more particularly, to an LTCC composition characterized by an excellent strength and a shrinkage-retardant effect in a planar direction, an LTCC substrate comprising the same, and a method of manufacturing the same.
2. Description of the Related Art
In general, a Low Temperature Co-fired Ceramic (LTCC) substrate using a glass-ceramic has high flexibility in terms of design because it allows the implementation of 3D-structural inter-layer circuits and the formation of cavities.
Multilayered ceramic substrates are increasingly utilized in a market of smaller and higher-functional HF components. As a multilayered ceramic substrate is structured to be complicated and precise, internal patterns and via structures have less margin in design. Thus, a non-shrinkage firing process has been required to suppress transverse shrinkage of the multilayered ceramic substrate.
To this end, flexible green sheets formed of a sinter-resistant material are bonded to one surface or both surfaces of a non-sintered ceramic substrate to suppress the shrinkage of the ceramic substrate in the x-y direction. Herein, the sinter-resistant material is not fired at a firing temperature of the material of the ceramic substrate.
However, constraint forces of the flexible green sheets bonded to the both surfaces of the ceramic substrate do not reach the center of the substrate as the ceramic substrate becomes increasingly thicker, which results in a reduction of an x-y directional shrinkage-retardant effect on the thick substrate.
A multilayered ceramic substrate made by stacking a plurality of ceramic green sheets is provided with a plurality of holes, which are used for electrical connection between interlayer circuits and filled with a conductive electrode material. At this time, since the via electrode is formed of a conductive metal powder, an organic binder, and a solvent, the via electrode shrinks in volume during the firing process. Herein, since the conductive metal power shrinks to a greater extent than the ceramic in the firing process, the via hole and the via electrode may be separated from each other due to the different firing shrinkage rate, creating large pores in the via hole, even in a case where the via hole is completely filled with the conductive electrode material before the firing process. In particular, while being subjected to the non-shrinkage firing process, the via electrode shrinks in the circumferential direction and thus shrinks less in the thickness direction because of the green sheets which serve to inhibit shrinkage in the non-shrinkage process but have a small shrinkage retardant effect on the non-sintered ceramic laminate. As a result, after being subjected to a firing process, the via electrode is higher than the via hole, thereby protruding toward the outside, and creating pores around the via hole.
In order to prevent pores from being formed around the via hole after the firing process, the via hole is filled with an excessive amount of conductive electrode material exceeding the volume of the via hole in a green state. This causes the unfilled conductive electrode materials to flow over the via hole during the laminating and pressurizing processes, resulting in short circuits between layers of the substrate or the delamination of the layers, degrading production yield.